This invention relates, in general, to transistors and, more particularly, to field effect transistors.
Radio frequency (RF) and microwave field effect transistors serve as low noise, linear radio frequency amplifiers in multi-channel receivers and transmitters. Although these transistors provide adequate gain and noise figure characteristics, they introduce intermodulation distortion for low drain current applications. Intermodulation distortion is caused by the non-linearities in the field effect transistors and degrades the quality of the amplified signal.
Several techniques are employed to reduce intermodulation distortion including a push-pull amplifier configuration, feedback, control of termination impedances at the second harmonic of the signal, and optimization of channel doping profiles. Most techniques for reducing intermodulation distortion require external circuitry or termination schemes, thereby increasing the cost and complexity of the multi-channel receivers and transmitters. Moreover, the processing changes for optimizing channel doping profiles are difficult to control.
Accordingly, it would be advantageous to have a low-cost technique for controlling intermodulation distortion that is readily incorporated into standard manufacturing techniques and can be integrated into the field effect transistor without requiring external circuitry.